Outdoor Research Alpine AscentShell Bivy
What is a Bivouac Sack?
The bivouac sack, or bivy sack, began as a temporary emergency shelter. It’s like a waterproof cover for a sleeping bag, but it also adds insulation and protects the user from the elements. In its most basic form, a bivy sack simply covers and protects.
Bivy sacks are not exactly like tents, although they do enclose you and your sleeping bag completely. Over time, however, the bivy has evolved into the shelter of choice for ultra-light campers and hikers.
Back to the main topic, let’s have a deeper look at the Outdoor Research Alpine AscentShell Bivy Sack.
- One benefit of a bivy is that it sets up much more quickly than a tent. There are usually loops for stakes, and they keep the structure in place.
- Bivy sacks provide more warmth than a tent because your body heat is retained inside. There’s also the benefit of layers that keep the warm air in: sleeping pad, sleeping bag, and bivy.
- A Bivy can be adapted for warm or cold weather by adjusting the weight of the sleeping bag inside.
- One drawback of a bivy over a tent is that there’s no room for gear, so it gets exposed to the elements.
- Condensation can be a problem in such a small space as well. Proper ventilation is important to keep moisture from building up inside.
- Sometimes a bivy can seem confining, which is why various makers have developed techniques to give some clearance room inside.
Key Features
Bivy sacks are the protection of choice for those who will be outside in the weather but need to travel light. This includes mountaineers, hikers and soldiers. Besides being lightweight, they’re easy to set up and they help you retain body heat in the cold. Here are some of the main features that a good bivy should have, and how the Outdoor Research Alpine Bivy stacks up.
Waterproofing
One of the two main features that users seek is waterproofing. The Alpine Bivy is made with Gore-Tex Respiration Positive membrane, a step up from the original Gore-Tex fabric. It allows water vapor to vent through the fabric without letting rain or snow inside.
Insulation
Protection from the cold is the second most important feature that users look for. Most bivvy sacks add a few degrees of insulation from the outdoors. Combined with your body heat, this makes it warm enough to sleep even when it’s cold outside.
Ease of Setup
One of the benefits of a bivy over a tent is quick setup. The Alpine rolls out easily and there are straps inside to secure the sleeping pad. A cell phone, watch and other small items can be stashed in the mesh bag attached to the inside. Loops and stakes are usually included to hold the bivy in place. The Alpine has five stake loops and a guy line loop.
Comfort
Having the right sleeping bag pad is one way to ensure the most comfort. It’s also important to have a bivy that’s large enough for your needs. The Alpine bivy includes a flexible pole that threads into the top of the shelter to keep the material off your face.
Ventilation
Because of the small enclosed space, bivy sacks can be prone to having condensation inside. Some ways of dealing with this are adding vents and covered zippers that can be partially opened. The Alpine’s flexible frame helps provide more breathing space, which also helps prevent condensation.
Weight/Compactness
The weight and compactness of a bivy determine whether it can be used for hiking and mountaineering or just as a shelter for light camping. The ones that we’re reviewing include lightweight stakes. This adds a bit to the load, but it’s well worth it for keeping a bivy in one place.
Cost
One thing to take into account with the cost is whether the bivy is part of a set that includes a sleeping bag, or if it only includes the outer cover.
How to Set up a Bivy Sack
Outdoor Research provided a video on how to set up their bivy sacks. This is especially useful if you are new to this type of shelter.
Detailed Review
Waterproofing – 5/5
The Alpine AscentShell Bivy uses AscentShell™ 3-layer fabric, which provides excellent waterproofing and breathability. The AscentShell material prevents condensation buildup while keeping water out, even in heavy rain. The Hydroseal® floor and fully taped seams ensure the bivy stays dry in wet conditions, offering advanced protection against moisture.
Insulation – 5/5
While the Alpine AscentShell Bivy can help trap body heat, its primary focus is on breathability and weather protection. You may experience some extra warmth, but the bivy’s real strength is managing condensation and staying dry rather than adding significant insulation.
Ease of Setup – 4.5/5
The loops provided allow you to stake the Alpine AscentShell Bivy, adding tension to maintain its shape and keep it in place. While it takes a few minutes to stake the bivy, doing so makes it easier to slide your sleeping pad and bag inside. Maintaining the shape also helps the flexible pole keep the head space available.
Comfort – 4.5/5
Any bivy is going to be a tight space, which some outdoor enthusiasts find confining. The head space provided in the Alpine AscentShell Bivy helps alleviate this sensation. It’s large enough to fit a 6.5-foot person and provides room for small essentials like shoes or a pillow, helping you avoid that cramped feeling.
Ventilation – 5/5
The Alpine AscentShell Bivy excels in ventilation. The no-see-um mesh over the head area keeps even the smallest insects out while allowing for great airflow. Even during rainy weather, the overlapping fabric and zippers maintain ventilation, reducing the risk of condensation while keeping you dry.
Weight & Packed Size – 5/5
This bivy is impressively lightweight and compact when packed, making it ideal for ultralight backpacking, climbing, or mountaineering trips. It won’t add much bulk or weight to your pack, ensuring that it’s easy to carry on longer adventures.
Cost – 3/5
While the Alpine AscentShell Bivy is a high-performing piece of gear, its advanced materials and design come at a higher price point. It’s considered an investment for those seeking reliable weather protection in a lightweight package.
How Does It Compare To Others?
Military Modular Sleep System
This model provides superior insulation compared to the others. Part of the reason is that, as the name states, it’s a modular system. The MM comes with two custom fitted sleeping bags, a lighter and heavier one, and they can be used together. Users have reported camping in near-freezing weather with only the MM as protection and staying warm all night.
The bivy itself requires no setup. The system of three compression/sleeping bags is fairly straightforward, with the pieces snapping together to keep them from getting tangled up.
The Military Modular is comfortable to sleep in, but it doesn’t have the pole support to keep the material off your face. It also has a limit to the size of the user, up to about a 6-foot-tall male.
This bivy isn’t as well-ventilated as some of the others. It zips completely closed, ‘mummy-style’, without vents. This also leads to problems with condensation.
Weight is not as light as the Alpine Bivy so if this might not be a great choice if you are doing ultra-light backpacking.
Snugpak 92860 Stratosphere
With a sleeping bag and mat, the bivy compares to army issue equipment as far as excellent insulation from the cold, even in near-freezing temperatures.
The Snugpak rolls out easily and has loops to stake it to the ground. There are two canopy poles that snap into place easily. The zipper down the side makes it easier to get in and out of the bivy. The unit is also easy to take down and pack up and takes up very little space.
The Snugpak canopy has two poles, providing more flexibility for arranging the space above. It will fit up to a 6-foot male comfortably, and it includes a mesh screen to keep out bugs. It’s roomy enough inside to keep a small pack and a weapon, as well as shoes. There’s also a mesh bag for a lantern or small items. In an emergency situation, two people could possibly fit inside.
The Snugpak has a mesh ventilation area at the back of the bivy that helps prevent condensation inside the bag. There’s also a vent in the head area with a fly cover that stakes down to prevent rain from getting in.
The weight of this bivy is higher than the rest so you might want to look elsewhere if you consider weight as an important factor.
Aqua Quest Hooped Bivy Tent
The insulation is excellent, and users have slept in a sleeping bag inside the bivy in complete comfort during near-freezing temperatures.
The Aqua Quest is fairly easy to set up, but it does take time to stake it out to give the extra room inside.
The head and shoulder area is raised with a hoop and gives more clearance than any of the others, with about 3 inches of headroom. The Aqua Quest will fit up to a 6.5-foot male comfortably and it has a bug mesh panel as well as a clear panel to look outside the shelter. The tie-down system has stiffeners in the foot area to keep the fabric away from your legs.
The mesh bug netting is more than just a panel. It covers the entire top third of the bivy, creating great ventilation during warm weather. An air vent is also included in the head section.
Looks like Alpine Bivy is the lightest as compared to the rest so definitely consider it if you are looking for a lightweight bivy.
Should you buy?
The ratings alone do not paint a picture of which product is the best for you. It depends on how much protection and space you need, for one thing. We gave the Outdoor Research Alpine AscentShell Bivy an almost perfect score with our 5-point rating system. It has an average weight and compactness compared to other bivy-only setups. However, it’s pricier than similar products.
A less expensive model, the Snugpak, also got a perfect score. The slightly narrower frame is offset by the ease of getting in and out with the side zipper of the Snugpak. It also has a pole system to keep the fabric off your head and shoulders, and it’s more flexible. There are two poles included, and they stay in place because they are staked.
The best feature of the Aqua Quest is the extra-large netting and clear panel that allow visibility even when zipped inside. Although it takes a bit more effort to set up, this bivy does best at adding room above and is somewhat of a bivy/tent hybrid.
The Military Modular is different from the other brands because it includes customized bedding. This is a big plus in keeping warm and it makes the MM the best choice if you really need to rough it in cold weather.
All of the selections are highly rated for warmth in winter and for waterproofing. For warmer weather, the Snugpak and Military Module would be too hot and clingy. However, the Alpine and the Aqua Quest provide enough roominess and ventilation to be used with only a light covering inside in the summer.
